13.10. Real-Time Communications software

Debian provides a wide range of Real-Time Communications (RTC) client software. The setup of RTC servers is discussed in 第 11.8 节 “Real-Time Communication Services”. In SIP terminology, a client application or device is also referred to as a user agent.

Each client application varies in functionality. Some applications are more convenient for intensive chat users while other applications are more stable for webcam users. It may be necessary to test several applications to identify those which are most satisfactory. A user may finally decide that they need more than one application, for example, an XMPP application for messaging with customers and an IRC application for collaboration with some online communities.

To maximize the ability of users to communicate with the wider world, it is recommended to configure both SIP and XMPP clients or a single client that supports both protocols.

The default GNOME desktop includes the Empathy communications client. Empathy can support both SIP and XMPP. It supports instant messaging (IM), voice and video. The KDE desktop provides KDE Telepathy, a communications client based on the same underlying Telepathy APIs used by the GNOME Empathy client.

Popular alternatives to Empathy/Telepathy include Ekiga, Jitsi, Linphone, Psi and Ring (formerly known as SFLphone).

Some of these applications can also interact with mobile users using apps such as Lumicall on Android.

Some RTC clients have significant problems sending voice and video through firewalls and NAT networks. Users may receive ghost calls (their phone rings but they don't hear the other person) or they may not be able to call at all.

The ICE and TURN protocols were developed to resolve these issues. Operating a TURN server with public IP addresses in each site and using client software that supports both ICE and TURN gives the best user experience.

If the client software is only intended for instant messaging, there is no requirement for ICE or TURN support.

Debian Developers operate a community SIP service at rtc.debian.org. The community maintains a wiki with documentation about setting up many of the client applications packaged in Debian. The wiki articles and screenshots are a useful resource for anybody setting up a similar service on their own domain.